In the manufacture of patterned devices, such as semiconductor chips and chip carriers, the processes of etching different layers which constitute the finished product are among the most crucial steps involved. One method widely employed in the etching process is to overlay the surface to be etched with a suitable mask and then to immerse the substrate and mask in a chemical solution which attacks the substrate to be etched while leaving the mask intact. These wet chemical processes suffer from the difficulty of achieving well-defined edges on the etched surfaces. This is due to the chemicals undercutting the mask and the formation of an isotropic image. In other words, conventional chemical wet processes do not provide the selectivity of direction (anisotropy) considered necessary to achieve optimum dimensional consistent with current processing requirements.
Moreover, such wet etching processes are undesirable because of the environmental and safety concerns associated therewith.
Accordingly, various so-called "dry processes" have been suggested to improve the process from an environmental viewpoint, as well as to reduce the relative cost of the etching. Furthermore, these "dry processes" have the potential advantage of greater process control and higher aspect ratio images.
Such "dry processes" generally involve passing a gas through a container and creating a plasma in this gas. The species in this gas are then u: ed to etch a substrate placed in the chamber or container. Typical examples of such "dry processes" are plasma etching, sputter etching, and reactive ion etching.
Reactive ion etching provides well-defined, vertically etched, sidewalls. A particular reactive ion etching process is disclosed, for example, in U.S. Pat. No. 4,283,249 to Ephrath, disclosure of which is incorporated herein by reference.
Examples of some dry-developable resists are provided in U.S. Pat. Nos. 4,426,247 to Tamamura, et al.; 4,433,044 to Meyer, et al.; 4,357,369 to Kilichowski, et al.; 4,430,153 to Gleason, et al.; 4,307,178 to Kaplan, et al.; 4,389,482 to Bargon, et al.; and 4,396,704 to Taylor. In addition, German patent application No. OS32 15082 (English language counterpart British patent application No. 2097143) suggests a process for obtaining negative tone plasma resist images. Such is concerned with a process involving entrapment of a silicon-containing monomer into a host film at the time of exposure to radiation and requires a processing step to expel the unincorporated silicon monomer from the film before plasma developing of the relief image.
A more recent example of a plasma developable resist is described in U.S. patent application Ser. No. 609,690 (assigned to the assignee of the present application) in which a method is provided for obtaining a resist which is stated to be radiation sensitive and oxygen plasma developable. Such process involves coating a substrate with a film of a polymer that contains a masked reactive functionality; imagewise exposing the film to radiation under conditions that cause unmasking of the reactive functionality in the exposed regions of the film; treating the exposed film with a reactive organometallic reagent; and then developing the relief image by treatment with an oxygen plasma. The specific organometallic reagents described therein are trimethylstannyl chloride, hexamethyldisilazane, and trimethylsilyl chloride. All of these materials are monofunctional.
In addition, a method of obtaining a two-layer resist by top imaging a single layer resist is described in U.S. patent application Ser. No. 679,527 (FI9-84046, assigned to the assignee of the present application) which also employs a monofunctional organometallic reagent.
The disclosures of the above two U.S patent applications are incorporated herein by reference.